--- a/hotspot/src/share/vm/c1/c1_LIRAssembler.cpp	Wed Sep 19 16:50:26 2012 -0700
+++ b/hotspot/src/share/vm/c1/c1_LIRAssembler.cpp	Thu Sep 20 16:49:17 2012 +0200
@@ -773,6 +773,11 @@
       throw_op(op->in_opr1(), op->in_opr2(), op->info());
       break;
 
+    case lir_xadd:
+    case lir_xchg:
+      atomic_op(op->code(), op->in_opr1(), op->in_opr2(), op->result_opr(), op->tmp1_opr());
+      break;
+
     default:
       Unimplemented();
       break;